Hepatitis D virus (HDV) infection is the most severe type of viral hepatitis, often causing accelerated liver damage that leads to end-stage liver disease. About 10-15 million individuals are infected by HDV worldwide. The absence of an effective treatment for acute forms of the disease and the limited efficacy of current treatments for the chronic infection justify novel strategies towards the development of anti-HDV therapeutics. The lack of HDV-encoded druggable targets that are suitable for conventional therapeutic modalities such as small molecules and antibodies makes RNA interference an attractive alternative approach to target this virus. In this Phase I SBIR proposal, we propose to develop anti-HDV inhibitors using a platform developed by SomaGenics for its hepatitis C program in which chemically modified, synthetic small shRNAs (sshRNAs), formulated with lipid nanoparticles, produced effective viral knockdown in preclinical animal models. To effectively inhibit HDV replication, we plan to develop sshRNAs against all three RNA species generated during viral replication. These sshRNA inhibitors will be identified using a cell-based HDV replication assay. The efficacy of these sshRNA inhibitors, individually and in combination, will be validated in a transgenic mouse model. The proposed studies should help identify the best RNA targets for RNAi therapeutic approaches to HDV as well as provide leads for further development as anti-HDV therapeutics.